1. Field of the Invention
The present invention relates to magnetic gauging systems, and more particularly, to an apparatus for gauging the thickness of coatings on metal products.
The invention can find advantageous application in gauging the thickness of nickel coatings on ferromagnetic and nonmagnetic bases, as well as for gauging the thickness of nonmagnetic coatings on ferromagnetic base.
2. Description of the Prior Art
There is known an apparatus for gauging the thickness of coatings on metal products, wherein the thickness gauged by a permanent magnet is indicated as a function of the force required to attract this magnet to the product being gauged (cf. U.S. Pat. No. 3,716,779; Cl G 01B). This apparatus comprises a wheel system, a spring drive linked to the wheel system so as to enable its rotation; two levers balanced in a static state, one of which mounts a permanent magnet interacting through its field with the ferromagnetic coating of a product or with the base thereof in case of a nonmagnetic coating, the other lever interacting with the first lever in the event when its force necessary to break away the permanent magnet from the product being gauged is insufficient; two coiled springs, the first of each is connected through one end thereof with the first lever and through the other end with one of the shafts of the wheel system, the second of the two coiled springs being linked through one of its ends with the second lever and through the other end thereof with a spring tensioning control means; a magnetic element adapted to attract the permanent magnet after it has broken away from the product being gauged; a reset lever intended for returning the first lever to its initial position and rigidly secured to the central shaft of the wheel system, the former mounting a winding knob and a pointer for indicating a gauged thickness on a round scale.
When the apparatus is wound for gauging by means of the winding knob, the end of the magnet moves below the bearing plane of the apparatus and the wheel system is locked.
When the bearing surface of the apparatus is placed on the surface to be gauged, the end of the magnet lowers flush with the bearing surface and the wheel system is actuated by the spring drive. As this happens, the first coiled spring is wound until the permanent magnet is broken away from the product being gauged. As the permanent magnet breaks away from the surface being gauged, the first lever turns about its axis and the break spring fixed thereon is actuated to stop a break wheel incorporated in the wheel system, as well as the wheel system as a whole.
After the permanent magnet has broken away from the product being gauged, the former is attracted by means of the mangetic element provided to assure more reliable locking.
The additional lever as well as the second coiled spring extend the overall range of thicknesses covered by the apparatus. However, the apparatus is unsuitable for correcting the force of attraction of the permanent magnet, this being the reason for short service life thereof due to premature demagnetization of the permanent magnet caused by interfering fields.
It is an object of the present invention to provide an apparatus for gauging the thickness of coatings on metal products, wherein a means is provided for correcting the attractive force of a permanent magnet to thereby ensure a higher degree of accuracy and longer service life of the apparatus.
The invention provides an apparatus for gauging the thickness of coatings on metal products, comprising a casing accommodating: a wheel system, a spring actuator with a means for its winding linked to the wheel system so as to enable its rotation, two levers independently balanced in a static state, the first of which carries a permanent magnet interacting through its field with a ferromagnetic coating on a product or with the base thereof in case of a nonmagnetic coating, the second of the two levers interacting with the first lever in the event when its force necessary to break away the permanent magnet from the product being gauged is insufficient; two coiled springs, the first of which is connected through one end thereof with the first lever and through the other end with one of the shafts of the wheel system, the second of the two coiled springs being connected through one of its ends with the second lever and through the other end thereof with a spring tensioning control means; a magnetic element attached to the casing and adapted to attract the permanent magnet after the latter has broken away from the product being gauged; a reset lever intended for returning the first lever to its initial position and linked to the central shaft of the wheel system, the former mounting a pointer for indicating readings on a round-shaped scale rigidly secured to the casing, according to the invention, there is provided an adjusting shunt mounted in the casing for movement along the permanent magnet and intended for correcting the attractive force of the latter.
Such apparatus construction makes it possible to improve accuracy and enhance service life of the apparatus due to the possibility of correcting the attractive force of the permanent magnet.
The adjusting shunt is preferably provided with a plate half-embracing the permanent magnet movably mounted on a screw positioned in the casing, and an arrester intended for limiting the movement of said plate.
Such adjusting shunt is simple in construction and is readily adaptable to gauging the thickness of a wide variety of metal coatings.
Where the apparatus is used for gauging the surface of a predetermined thickness, the adjusting shunt is provided in the form of a ring surrounding the permanent magnet and retained thereon by force of friction .